1. Field of the Invention
The present invention relates to an electronic component. More specifically, the present invention relates to an electronic component having a plate-shaped element, such as a ceramic resonator, a ceramic filter or an integrated circuit element.
2. Description of the Prior Art
FIG. 1 and FIG. 2 shows a filter element which is part of the background of the present invention. FIG. 1 is a front view thereof, and FIG. 2 is a rear view thereof. A filter element 10 as shown in FIG. 1 and FIG. 2 is an energy-trapping type piezoelectric filter utilizing a thickness-sliding vibration mode (shear mode). Since the present invention is suitable particularly for such a piezoelectric filter, a description will be made of this filter element to the extent required for understanding the present invention.
The element 10 comprises a strip-shaped piezoelectric substrate 12 composed, for example, of a piezoelectric ceramic materials, and on this piezoelectric substrate 12, a slit 13 is formed from the top end thereof to nearly the center thereof in the direction of a longer side. Also, on both the right and the left sides of a front main surface of the piezoelectric substrate 12 divided by the slit 13, two pairs of vibrating electrodes 14a and 14c1, on the left side and 14b and 14c2 on the right side, are formed, respectively. Among the right and the left vibrating electrodes, the electrodes 14c1 and 14c2 are connected in common. On the rear main surface of the piezoelectric substrate 12, common electrodes 16a and 16b are formed opposite to respective pairs of vibrating electrodes 14a and 14c1, and 14b and 14c2.
Also, on the front main surface of the piezoelectric substrate 12, a drawing-out part 18a formed which extends to the top end of the piezoelectric substrate 12 from the vibrating electrode 14a and a drawing-out part 18b is formed which extends to the top end of the piezoelectric substrate 12 from the vibrating electrode 14b. Furthermore, on the other (rear) main surface of the piezoelectric substrate 12, the common electrodes 16a and 16b are connected in common to form a drawing-out part 20 which extends to the bottom end of the piezo-electric substrate 12. These electrodes and drawing-out parts are formed, for example, by metallizing or sputtering silver, nickel or the like.
At least one lead terminal is connected to such a filter element 10. More specifically, as shown in FIG. 3, a lead terminal 22 is connected to the drawing-out part 20, a lead terminal 24a to the drawing-out part 18a and a lead terminal 24b to the drawing-out part 18b respectively, for example, by means of soldering.
Furthermore, as shown in FIG. 4, the filter element 10 to which the lead terminals 22, 24a and 24b are connected is coated with an elastic material 26 such as silicone rubber or the like, and is further coated with a sheathing member 28 such as resin or the like, thus forming a piezoelectric filter 30 having a circuit configuration as shown in FIG. 5.
In this piezoelectric filter 30, the filter element 10 floats in the elastic material 26 even after completion, and needless to say, during manufacturing, and therefore the element 10 has sometimes been broken by an external shock. Particularly, this breakage has taken place in filters in which the slit 13 was formed at the center of the piezoelectric substrate 12 of the element 10.
In order to prevent such a crack or split of the piezo-electric substrate 12, as shown in FIG. 6, use of a reinforcing substrate 40 has been proposed. More specifically, conductor patterns 42, 44a and 44b corresponding to respective tip portions of the lead terminals 22, 24a and 24b in FIG. 3 are formed on the surface of a reinforcing substrate 40 composed of an insulating material. The filter element 10 is placed on this reinforcing substrate 40, and one end of each of the conductor patterns 42, 44a and 44b is connected to a respective one of the drawing-out parts 20, 18a and 18b of the element 10, for example, by means of soldering. Then, the lead terminals 22, 24a and 24b are connected to each of the other ends of the conductor patterns 42, 44a and 44b, for example, by means of soldering.
In this prior art filter, the mechanical strength is great enough that no crack or the like of the element takes place, but it requires preparation of a reinforcing substrate whereon a predetermined conductor pattern is formed as a separate part. Thus not only the number of parts is increased but also the number of places to be soldered is increased, and also the manufacturing process becomes more complicated, resulting in higher cost. Furthermore, since the conductor patterns are required to be formed on the reinforcing substrate, the reinforcing substrate cannot be made smaller than the element, so this prior art filter cannot easily be miniaturized.